If there is a lot of pranking going on in the office, sometimes people come to expect it. They try to stay late in their office the night before a personal milestone, or show up early after a vacation to scope things out before their office mates get in.
We like to keep them guessing.
Kelly's birthday was this week and she's seen us prepare many of our recent cubicle escapades, so we're sure she was expecting to walk in that morning and see the surfaces of her desk covered in elmo fur or hermit crabs or something similar. However, we remembered that she is getting married in just 3 months - and what a good opportunity to get this beloved coworker paranoid about what we'll do while she's on her honeymoon.
Along with the seemingly random jelloed stapler, we left this poem at her desk:
You thought you may have figured us out
But what fun would there be if there were no doubt?
We bring a special birthday gift for you
A little something from the zoo
So here we present this fine giraffe
Who brings this message on our behalf
This giraffe is just the start
The full reveal requires more take part
We wish you well on your honeymoon
We'll see you soon, perhaps May or June
And, sitting next to it, was a giraffe balloon animal.
The Teaser Prank
Leave a seemingly random item with a seemily random poem. Let them think something else bigger and scarier is coming. Watch them squirm.
We're sure you saw the stapler in Jello on The Office, when Jim did this to Dwight so we thought we'd show you how easy it is to do. This is a fun and easy prank that requires no special occasion other than needed a good laugh. Especially great if a co-worker is really attached to their stapler. Those with red swingline staplers are excellent targets for this one. 

success for these kinds of pranks are 80% thoroughness/attention to detail. And these pranksters never settle for 2nd best.